This invention relates to a stack elevating apparatus for a sheet feeder and to a reproducing apparatus including the stack elevator and sheet feeder. The stack elevating apparatus is adapted to provide rapid lowering to a reloading position. An inertial control system is utilized to regulate the rate at which the elevator descends to the reloading position.
A wide variety of sheet stack elevating apparatuses have been devised in accordance with the prior art, as set forth, for example, in U.S. Pat. No. 2,076,186 to Reynolds, et al.; U.S. Pat. No. 2,368,094 to Baker et al.; U.S. Pat. No. 2,141,418 to Sinkovitz; and U.S. Pat. No. 3,843,115 to DiFulvio, et al. The stack elevator arrangements which are illustrated in those patents provide various combinations of slow raising and fast lowering and visa-versa, for the stack support platform.
One prior art system of particular interest is set forth in U.S. Pat. No. 3,301,551 to Cassano, et al. This system is utilized with a xerographic copier. The stack elevator for the sheet feeder is designed to provide slow raising of the elevator for feeding sheets, and fast lowering of the elevator by gravity through disengagement of the drive motor from the elevator drive gear.
It is also known in the art to utilize a single drive motor for coordinating the drive of an imaging surface and a sheet feeding apparatus. This is illustrated in U.S.. Pat. No. 3,033,110 to Keil, and in a variety of commercially employed xerographic copying machines such as the Xerox 3100 copier. In the latter machine a single drive motor is utilized to drive both the imaging drum and the paper feeder with the latter being intermittently driven through the use of a suitable clutch mechanism.
The stack elevating devices of the prior art are undoubtedly useful for their intended purposes. It has been found desirable to provide a stack elevating device which is capable of being rapidly lowered to its reloading position as in the Cassano et al. patent, but which further includes some means for controlling the rate at which the stack support descends. If it descends at too rapid a rate a high impact force results as it reaches the lowered position. Further, it is desirable to reduce the difference in the rate of descent irrespective of whether the stack support elevator tray is fully loaded, partially loaded, or nearly empty. It is also desired to provide a stack elevating apparatus which is inexpensive and not very complex in design.